The present invention refers to a method of producing a fibrous material layer mainly intended to be incorporated in an absorbent article such as a diaper, pant diaper, incontinence guard, sanitary napkin or the like.
Absorbent articles of the above mentioned kind are intended to absorb body liquids such as urine and blood. They usually comprises a liquid pervious topsheet, intended to be facing the wearer during use, in the form of a nonwoven material for example a spunbond material. It is also known to incorporate a liquid acquisition layer between the topsheet and the absorbent body, said liquid acquisition layer having the ability to quickly receive large amounts of liquid, to distribute it and temporarily store it before it is absorbed by the underlying absorbent body. This is important especially in today""s thin compressed absorbent bodies often with a high amount of so called superabsorbents, which have a high absorption capacity but in many cases a too low absorption speed in order to momentaneously be able to absorb the large amount of liquid that can be discharged during a few seconds at urination.
A porous relatively thick acquisition layer, for example in the form of a fibrous wadding, a carded fibrous web or other type of fibrous material has a high momentaneous liquid receiving capacity and can temporarily store liquid before it is absorbed by the absorbent body. The same applies for porous foam materials. The liquid is then drained successivley to the underlying absorbent body, after which the acquisition layer again has capacity to receive liquid from a repeated wetting.
Examples of absorbent articles comprising such porous acquisition layer are for example disclosed in U.S. Pat. No. 3,371,667, EP-A-0,312,118 and EP-A-0,474,777.
The materials used today as acquisition layers in absorbent articles are mostly functioning well but are relatively expensive and can sometimes have an insufficient acquisition time, especially at the second and third wettings if large amounts of liquid are involved.
It is previously known through EP-A-0,391,814 and GB-B-2,209,672 to use continuous nonbonded synthetic fibers, so called tow, in absorbent articles to spread liquid in the longitudinal direction of the article.
Another problem is that conventional liquid pervious topsheet materials used for absorbent articles of this kind, usually a nonwoven material of synthetic fibers, e g a spunbond material, often has a lower acquisition rate for liquid than the acquisition layer, at which liquid can leak from the article before it reaches the acquisition layer. The problem can of course be solved by using a topsheet material which is very open and by that has a high liquid permeability. Such an open topsheet material can however cause problems with a too low strength and sharp fiber ends from the acquisition layer may penetrate the open topsheet material and irritate the user.
The object of the present invention is to provide a method of producing a fibrous material layer having a high acqusition rate for liquid also at repeated wettings, has a high strength and wear resistance, high comfort and can be produced at a low cost. The method should besides be adapted to high production speeds. This has according to the invention been provided by taking at least one bundle of continous filaments, so called tow, which is opened and the filaments are separated and evened to a layer having the desired fiber distribution, after which the layer is bonded in points, spots or lines in a bonding pattern, but where the filaments otherwise are substantially unbonded to each other.
Further features of the invention are evident form the following claims and from the description.
The material layer can be used as a liquid acquisition layer under a topsheet material, as a topsheet material or as an integrated topsheet/liquid acquisition layer.